Dissertations / Theses on the topic 'Nasal aerodynamics'

An enlarged nasopharyngeal tonsil, curvature of the nasal septum and chronic rhinosinusitis and other disorders causing difficulty in nasal breathing, but the violation of breathing through the nose can be in the usual runny nose, and when foreign bodies get into the nasal passages. Objective information about the physiological processes occurring in the nasal airways allows us to select a suitable treatment strategy based on functional information.

There is studing the most important aerodynamic processes occurring in the nasal airway specifically with breathing disorders, and to identify the most important respiratory functions of the upper respiratory system

Hypersonic flight at sea-level conditions induces severe thermal loads not seen by any other type of current hypersonic system. Appropriate design of the hypersonic round requires a solid understanding of the thermal environment. Numerous codes were obtained and assessed for their applicability to the problem under study, and outside of the GASP Conjugate Heat Transfer module, Navier-Stokes code from Aerosoft, Inc., no efficient codes are available that can model the aerodynamic heating response for a fully detailed projectile, including all subassemblies, over an entire trajectory. Although the codes obtained were not applicable to a fully detailed thermal soak analyses they were useful in providing insight into ablation effects. These initial trade studies indicated that ablation of up to 1.25 inches could be expected for a Carbon-Carbon nosetip in this flight environment. In order to capture the thermal soak effects a new methodology (BMA) was required. This methodology couples the Sandia aerodynamic heating codes with a full thermal finite element model of the desired projectile, using the finite element code ANSYS from ANSYS, Inc. Since ablation can be treated elsewhere it was not included in the BMA methodology. Various trajectories of quadrant elevations of 0.5, 10, 30, 50, and 80 degrees were analyzed to determine thermal time histories and maximum operating temperatures. All of the trajectories have the same launch condition, Mach 8 sea-level, and therefore will undergo the same initial thermal spike in temperature at the nose-tip of approximately 3,100 K (5600R). Of the five trajectories analyzed the maximum internal temperatures experienced occurred for the 50 degree quadrant elevation trajectory. This trajectory experienced temperatures in excess of 1,000 K (1800R) for more than 80% of its flight time. The BMA methodology was validated by comparisons with experiment and computational fluid solutions with an uncertainty of 10% at a cost savings of over three orders of magnitude.
Ph. D.

Computational fluid dynamics methods have seen an increasing role in aerodynamic analysis since their first implementation. However, there are several major limitations is these methods of analysis, especially in the area of modeling separated flow. There exists a large demand for high-fidelity experimental data for turbulence modeling validation. Virginia Tech has joined NASA in a cooperative project to design and perform an experiment in the Virginia Tech Stability Wind Tunnel with the purpose of providing a benchmark set of data for the turbulence modeling community for the flow over a three-dimensional bump. This process requires thorough risk mitigation and analysis of potential flow sensitivities. The current study investigates several aspects of the experimental design through the use of several computational fluid dynamics codes. An emphasis is given to boundary condition matching and uncertainty quantification, as well as sensitivities of the flow features to Reynolds number and inflow conditions. Solutions are computed for two different RANS turbulence models, using two different finite-volume CFD codes. Boundary layer inflow parameters are studied as well as pressure and skin friction distribution on the bump surface. The shape and extent of separation are compared for the various solutions. Pressure distributions are compared to available experimental data for two different Reynolds numbers.
Master of Science
Computational fluid dynamics (CFD) methods have seen an increasing role in engineering analysis since their first implementation. However, there are several major limitations is these methods of analysis, especially in the area of modeling of several common aerodynamic phenomena such as flow separation. This motivates the need for high fidelity experimental data to be used for validating computational models. This study is meant to support the design of an experiment being cooperatively developed by NASA and Virginia Tech to provide validation data for turbulence modeling. Computational tools can be used in the experimental design process to mitigate potential experimental risks, investigate flow sensitivities, and inform decisions about instrumentation. Here, we will use CFD solutions to identify risks associated with the current experimental design and investigate their sensitivity to incoming flow conditions and Reynolds number. Numerical error estimation and uncertainty quantification is performed. A method for matching experimental inflow conditions is proposed, validated, and implemented. CFD data is also compared to experimental data. Comparisons are also made between different models and solvers.

Os estudos de caracterização acústica das vogais nasais são vastoa. Porém, há poucos estudos sobre a ditongação nasal. Este é um fenômeno que emerge da costelacao articulatória dos gestos. Isso pode ser notado a partir dos parâmetros acústicoaerodinâmicos. O objetivo desta é analisar o resultado da configuração gestual entre o movimento da língua e o gesto de abertura e fechamento do véu palatino, durante a produção dos ditongos nasais do Português Brasileiro. Mostraremos os efeitos da coarticulação no output sonoro e como ela se configura, a partir da gravação de dados acústicos e aerodinâmicos. O material foi gravado com o aparelho EVA Portátil 2. Esse permitiu que o output acústico e os dados aerodinâmicos fossem gravados concomitantes. O corpus do experimento é composto por vinte ditongos divididos em orais e nasais (dez posteriores e dez anteriores) todos dicionarizados: [p@w, s@w, m@w, k@w, t@w,p@)w), s@)w), m@)w), k@)w), t@)w), dej, sej, frej, hej, lej, te)j ), se)j ,) be)j ), a.mej), a.le)j\\) . As palavras foram inseridas na frase-veículo: Digo _____ cada dia. Essa foi repetida três vezes por seis informantes (três homens e três mulheres) falantes do dialeto Paulistano ( ). Para o controle de população foi utilizada outra frase-veículo: Digo ____ todo dia, essa foi repetida por 1.3 dos sujeitos, um de cada grupo ( ). Na inspeção visual utilizou-se o software Signal Explorer e Phonédit. Os parâmetros aerodinâmicos analisados foram: a configuração do fluxo de ar oral e nasal; a taxa máxima de nasalização e a duração do fluxo de ar nasal. Os parâmetros acústicos foram: a movimentação dos formantes; a extração de F0, F1, F2 e F3 de todos os segmentos e a duração do ditongo nasal: a vogal, o glide e o apêndice nasal. A Média, o Desvio Padrão e o teste ANOVA foram feitos no Excel. Os gráficos de dispersão dos formantes foram feito no Formant Explorer. Assim, notou-se uma variação nos valores da taxa de nasalização, p > 0,5, entre a variante sexo. Nas mulheres as frequências dos formantes são mais elevadas e a dispersão dos valores do glide nasal é mais evidenciada do que nos homens. As alterações remetem as diferenças fisiológicas entre os grupos. A taxa máxima de ar nasal variou significativamente, p > 0,5, se comparado os ditongos nasais: anteriores > posteriores. Acusticamente, a transição dos formantes é dependente do contexto silábico. O mesmo não acontece com o traçado do fluxo de ar nasal, que mantém o padrão de contorno, independente da articulação silábica. Concluí-se que há um padrão aerodinâmico relativo à sincronia do movimento do véu e da língua, gerando três fases acústicas distintas: vogal nasal, glide nasal e apêndice nasal. O contorno da trajetória padrão do fluxo de ar nasal, em 87% dos casos, apresentou três fases distintas: a primeira plana; a segunda, um pico acentuado; e a terceira, uma queda abrupta. Assim, concluímos que os ditongos nasais têm uma dinâmica articulatória, acústica e aerodinâmica diferente dos não-nasalizados e que a adequação do controle das variáveis do sistema fonético-fonológico e do o conjunto de articulações, que geram uma única percepção.
There are several studies that characterize the nasal vowels. However, there are few studies about the nasal diphthongation. This phenomenon emerges from the articulatory gestures constellation. This can be noted by analyzing of the acousticaerodynamics parameters. The aim of this work is study the gesture configuration between the thong movement and the velum aperture during the nasal diphthongs production of the Brazilian Portuguese. We will show the effects of the coarticulation in the output and how it sets up in the acoustic and aerodynamic data. The data was recorded by the device EVA Portable 2. Thus, the airflow and the acoustic output were collected concomitantly. The corpus of this experiment was covered by ten oral and ten nasal diphthongs, between ten back and ten front:[p@w, s@w, m@w, k@w, t@w,p@)w), s@)w), m@)w), k@)w), t@)w), dej, sej, frej, hej, lej, te)j ), se)j ,) be)j ), a.mej), a. le)j)\\. These words are dictionaries. They were inserted in the carry-sentence [dZi.gU__ ka.d5 dZi5] and were repeated three times, by six subjects (three men and three women); all of them are Paulistano Dialects speakers. This resulted in 360 tokens (3 × 6 × 20). The carry-sentence of the populational control was [dZi.gU__ to.dT dZi5]. This was repeated by 1/3 of the subjects. This resulted in 120 tokens (3 × 2 × 20 ). The diphthong was analyzed by Signal Explorer and Phonédit. The aerodynamic parameters studied were: the nasal and oral airflow shape; the peak of nasalization and the duration of nasal airflow. The acoustic parameters analyzed were: the movement and the configuration of the formants; the values of F0, F1, F2 and F3 were extracted of all segments; the nasal diphthongs duration in the vowel, the glide and the nasal appendix. The Average, Pattern Deviation and ANOVA were done by Excel. The dispersion graphics were made by Formant Explorer. As a result we noticed that the formants movements dependent on syllabic context. The womens formants had different values of males. The degree of the dispersion of hers was higher than him. This was showed more evident in the nasal glides. This reflects the physiological differences between the groups. The nasal airflow peak variation was p> 0,5 among the sex variant. The rate of nasal airflow of the back has more volume than front, dp > 0,5. The same does not happen with the nasal airflow shape. The shape pattern is independent of syllabic articulation, but the rate of nasalization depends of the articulation. We concluded that there is an aerodynamic pattern that is resulted of the thong movement and velum aperture. This product three distinct acoustic phases: vowel nasalization, glide nasal and the nasal appendix. By the aerodynamic view, in 87% of cases, the pattern shape of the nasal airflow represents three distinct phases: the first is sharp; the second is a peak; and last part is a drop line. Thus, we concluded that the nasal diphthongs have articulatory, acoustic and aerodynamic patters different from the non-nasalized segment. These reflect the adequacy of the control of variables of phonetic-phonological system and the set of these characteristics creates a single perception.

Dissertation (Ph.D.)--University of Toledo, 2010.
Typescript. "Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Doctor of Philosophy Degree in Engineering." "A dissertation entitled"--at head of title. Title from title page of PDF document. Bibliography: p. 152-156.

ITC/USA 2007 Conference Proceedings / The Forty-Third Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2007 / Riviera Hotel & Convention Center, Las Vegas, Nevada
The U.S. Army Research Laboratory (ARL) was requested by the National Aeronautics and Space Administration (NASA) Langley Research Center (LaRC) to perform a free-flight experiment with a telemetry (TM) instrumented sub-scaled Apollo shaped reentry vehicle in order to determine its aerodynamic coefficients. ARL has developed a unique flight diagnostic capability for reconstructing flight trajectory and determining aerodynamic coefficients of projectiles by using sensor data telemetered from free flight experiments. A custom launch package was designed for this experiment that included the Apollo shaped projectile, which housed a modular telemetry unit, and a rapid prototyped sabot. The experiment was able to produce estimates for aerodynamic coefficients that were considered accurate and this technique is appealing to NASA for the development of their spacecraft in the future.

In recent years, airports have experienced increasing airport congestion, partially due to the hub-and-spoke model on which airline operations are based. Current airline operations utilize large airports, focusing traffic to a small number of airports. One way to relieve such congestion is to transition to a more accessible and efficient point-to-point operation, which utilizes a large web of smaller airports. This expansion to regional airports propagates the need for next-generation low-noise aircraft with short take-off and landing capabilities. NASA has attacked this problem with a high-lift, low-noise concept dubbed the Cruise Efficient Short Take-Off and Landing (CESTOL) aircraft. The goal of the CESTOL project is to produce aircraft designs that can further expand the air travel industry to currently untapped regional airports. One method of obtaining a large lifting capability with low noise production is to utilize circulation control (CC) technology. CC is an active flow control approach that makes use of the Coanda effect. A high speed jet of air is blown over a wing flap and/or the leading edge of the wing, which entrains the freestream flow and effectively increases circulation around the wing. A promising tool for predicting CESTOL aircraft performance is computational fluid dynamics (CFD,) due to the relatively low cost and easy implementation in the design process. However, the unique flows that CC introduces are not well understood, and traditional turbulence modeling does not correctly resolve these complex flows (including high speed jet flow, complex shear flows and mixing phenomena, streamline curvature, and other challenging flow phenomena). The recent derivation of the v2-f turbulence model shows theoretical promise in increasing the accuracy of CFD predictions for CC flows, but this has not yet been assessed in great detail. This paper presents a methodical verification of several variations on the v2-f turbulence model. These models are verified using simple, well-understood flows. Results for CC flows are compared to those obtained with more traditional turbulence modeling techniques (including the Spalart-Allmaras, k-ε, and k-ω turbulence models). Wherever possible, computed results are compared to experimental data and more accurate numerical methods. Results indicate that the v2-f turbulence models predict some aspects of circulation control flow fields quite well, in particular the lift coefficient. The linear v2-f, nonlinear v2-f, and nonlinear v2-f-cc turbulence models have generated lift coefficients within 19%, 14%, and -26%, respectively of experimental values, whereas the Spalart-Allmaras, k-ε, and k-ω turbulence models produce errors as high as 85%, 36%, and 39%, respectively. The predicted stagnation points and pressure coefficient distributions match experimental data roughly as well as standard turbulence models do, though the modeling of these aspects of the flow do show some room for improvement. The nonlinear v2-f-cc turbulence model shows very non-physical skin friction coefficient profiles, pressure coefficient profiles, and stagnation points, indicating that the streamline curvature correction terms need attention. Regardless of the source of the discrepancies, the v2-f turbulence models show promise in the modeling of circulation control flow fields, but are not quite ready for application in the design of circulation control aircraft.

Simulation of a dynamic system is known to be sensitive to various factors and one of them could be the precision of model parameters. While the sensitivity of flight dynamic simulation to small changes in aerodynamic coefficients is typically not studied, the simulation of aircraft required to operate in nonlinear flight regimes usually at high angles of attack can be very sensitive to such small differences. Determining the significance and impact of the differences in aerodynamic characteristics is critical for understanding the flight dynamics and designing suitable flight control laws. This thesis uses this concept to study the effect of the differences in aerodynamic data for different aerodynamic models provided for a same aircraft which is F-18 HARV combat aircraft. The aircraft was used as a prototype for the high angles of attack technology program. However modeling an aircraft at high angles of attack requires an extensive aerodynamic data which are usually di cult to access. All aerodynamic models were collected from open literature and implemented within a nonlinear six degree of freedom aircraft model. Inspection of aerodynamic data set for these models has shown mismatches for certain aerodynamic derivatives, especially at higher angles of attack where nonlinear dynamics are known to exist. Nonlinear simulations are used to analyse three different types of flight dynamic models that use look-up-tables, arc-tangent formulation and polynomial functions to represent aerodynamic data that are suitable for high angles of attack application. To achieve this, a nonlinear six degree of freedom Simulink model was developed to accommodate these aerodynamic models separately. The trim conditions were obtained for different combinations of angles of attack and airspeed and the models were linearized in each case. Properties of the resulting state matrices such as eigenvalues and eigenvectors were studied to determine the dynamic behaviour of the aircraft at various flight conditions.

The circulation control system onboard Cal Poly's Advanced Model for Extreme Lift and Improved Aeroacoustics was a critical component of a highly complex wind tunnel model produced in order to fulfill the requirements of a NASA Research Announcement awarded to David Marshall of the Aerospace Engineering Department. The model was based on a next generation, 150 passenger, regional, cruise efficient, short take-off and landing concept aircraft that achieved high lift through circulation control wings and over-the-wing mounted engines. The wind tunnel model was 10-ft in span, used turbine propulsion simulators, and had a functioning circulation control system driven from tunnel supplied high pressure air. Wind tunnel test results will be compiled into an open-source database intended for validation of predictive tools whose purpose is to advance the state- of-the-art in predictive capabilities for the next generation aircraft configurations. The model's circulation control system produced highly directional, nonuniform flow, and required significant modification in order to generate flow suitable for representation in predictive software. The effort and methods used to generate uniform flow along the circulation control slots is detailed herein. Additionally the results of the system characterization are presented and include a thorough analysis of the slot height, the wing symmetry, and total pressure at the circulation control jet exit. These datasets are intended to aid in making adjustments to the simulation such that it accurately reflects the condition at which the model was tested. Many flow visualization results from the wind tunnel test are also presented to serve as a medium of comparison for results from predictive tools. Oil flow visualization was conducted at many test conditions and provides insight to AMELIA's surface flow in blown and unblown regions. Of particular interest were streamlines at the wingblend, which exhibited some outboard turning, and streamlines on the lower surface where the leading edge stagnation point was investigated. Smoke flow visualization was also utilized to explore the flowfield. The deflection of a individual streamline, under the influence of a changing discharge coefficient as investigated along with the discharge coefficients effect on the extended flowfield. Collectively, the images depict the massive augmentation of the flowfield caused by the presence of the circulation control wing.

Cette étude s’inscrit dans le cadre de l’application des connaissances acquises grâce à des expériences de phonétique expérimentale à l’enseignement de la prononciation des voyelles dans le cadre du FLE. Les formants des voyelles orales françaises et arabes prononcées par des natifs indiquent que les voyelles /iː aː uː/ de l’arabe diffèrent phonétiquement des /i a u/ du français, en particulier /iː uː/ qui se rapprochent plutôt de /e o/ du français. L’étude acoustique des voyelles du français montre que la voyelle /u/ perd son identité quand elle est réalisée par des apprenants jordaniens : les formants de /u/ réalisée par des débutants sont proches de /ø/ et ceux par des apprenants avancés sont proches de /o/. Les études perceptives confirment que /u/ est confondue avec /o ø/ et indique que les apprenants réalisent seulement un timbre des paires: [e-ɛ], [ø-œ] et [o-ɔ] et qu’ils réussissent à reproduire et identifier /y/ et /ø/ pourtant absentes de leur système phonologique. En revanche, les voyelles nasales représentent, pour eux, une grosse difficulté. Ils les confondent entre elles et avec des voyelles orales. L’étude aérodynamique des voyelles /ɑ̃ ɛ̃ ɔ̃/ des apprenants jordaniens montrent qu’ils synchronisent différemment l’arrivée du débit d’air nasal et qu’ils répartissent différemment sa quantité sur les voyelles par rapport aux natifs. La mesure des formants au début des voyelles nasales montre que les apprenants ne possèdent pas les mêmes cibles articulatoires pour /ɑ̃ ɛ̃ ɔ̃/ que les natifs. Notre thèse s’achève par une réflexion portant sur des stratégies de correction phonétique, des propositions matérielles et techniques d’entraînement à la prononciation
The dissertation deals with the application of knowledge acquired from experimental phonetics to the teaching of vowels pronunciation within the framework of French as a foreign language. The formants of French and Arabic oral vowels pronounced by natives indicate that Arabic vowels /iː aː uː/ differ phonetically from French /i a u/, in particular /iː uː/, which were realized more like /e o/ of French. The acoustic study of French vowels shows that the French /u/ loses its identity when it is produced by the Jordanian learners: The formants of /u/ realized by beginners are close to those of /ø/, and close to /o/ in the realization of advanced learners. The perceptive studies confirm that the learners merge /u/ with /ø o/ and reproduce only a single sound for the following pairs: /e-ɛ/, /ø-œ/ and /o-ɔ/ whereas they realize and identify correctly /y ø/ in spite of the absence of /y ø/ in their phonological system. By contrast, the nasal vowels /ɑ̃ ɛ̃ ɔ̃/ pose a serious problem for the learners. They are mutually merged and also confused with oral vowels. The aerodynamic study of French nasal vowels, pronounced by Jordanians learners indicates that they synchronize differently the onset of nasal airflow and distribute in different manner its quantity on the vowels with regard to the realization of natives. The formants measured at the beginning of /ɑ̃ ɛ̃ ɔ̃/ show that the learners do not have the same articulatory targets for the nasal vowels as the natives. The dissertation ends up with a reflection concerning strategies of phonetic correction, materials and technical propositions for pronunciation teaching

碩士
國立清華大學
語言學研究所
103
This thesis is an aerodynamic study of nasality and nasalization in Taiwanese Mandarin, with special reference to the following topics: i) nasality of nasal consonant and ii) contextual nasalization of vowels. In addition, the experimental results were compared with those of Mandarin Chinese and Taiwanese Southern Min. It appears that there are still some notable cross-dialectal differences. Finally, our results may also shed light on the disputed patterns of place neutralization in nasal codas in Taiwanese Mandarin.

碩士
國立清華大學
語言學研究所
99
This research aims at systematically investigate the aerodynamic and acoustic aspects of nasal vowels and nasalized vowels in Taiwanese, a language that has a nasality contrast in its vowels but are subject to stricter restrictions on nasality distribution than French. Our results show that i) the onset consonantal effects on nasal anticipatory coarticulation are subtly different between the two languages; ii) in onset positions, aspirated stops and fricatives induce more nasal coarticulation, iii) coda [n] triggers the least anticipatory vowel nasalization in both languages, iv) the production of nasal vowels are generally the same and vowel height is positively correlated with nasalization in both languages, v) that French has more nasal airflow volume than Taiwanese does. Taken together, our results confirm that phonological patterning does have a bearing on phonetic implementation

The purpose of this dissertation is to study the aeroelastic stability of a proposed flexible thermal protection system (FTPS) for the NASA Hypersonic Inflatable Aerodynamic Decelerator (HIAD). A flat, square FTPS coupon exhibits violent oscillations during experimental aerothermal testing in NASA's 8 Foot High Temperature Tunnel, leading to catastrophic failure. The behavior of the structural response suggested that aeroelastic flutter may be the primary instability mechanism, prompting further experimental investigation and theoretical model development. Using Von Karman's plate theory for the panel-like structure and piston theory aerodynamics, a set of aeroelastic models were developed and limit cycle oscillations (LCOs) were calculated at the tunnel flow conditions. Similarities in frequency content of the theoretical and experimental responses indicated that the observed FTPS oscillations were likely aeroelastic in nature, specifically LCO/flutter.

While the coupon models can be used for comparison with tunnel tests, they cannot predict accurately the aeroelastic behavior of the FTPS in atmospheric flight. This is because the geometry of the flight vehicle is no longer a flat plate, but rather (approximately) a conical shell. In the second phase of this work, linearized Donnell conical shell theory and piston theory aerodynamics are used to calculate natural modes of vibration and flutter dynamic pressures for various structural models composed of one or more conical shells resting on several circumferential elastic supports. When the flight vehicle is approximated as a single conical shell without elastic supports, asymmetric flutter in many circumferential waves is observed. When the elastic supports are included, the shell flutters symmetrically in zero circumferential waves. Structural damping is found to be important in this case, as "hump-mode" flutter is possible. Aeroelastic models that consider the individual FTPS layers as separate shells exhibit asymmetric flutter at high dynamic pressures relative to the single shell models. Parameter studies also examine the effects of tension, shear modulus reduction, and elastic support stiffness.

Limitations of a linear structural model and piston theory aerodynamics prompted a more elaborate evaluation of the flight configuration. Using nonlinear Donnell conical shell theory for the FTPS structure, the pressure buckling and aeroelastic limit cycle oscillations were studied for a single elastically-supported conical shell. While piston theory was used initially, a time-dependent correction factor was derived using transform methods and potential flow theory to calculate more accurately the low Mach number supersonic flow. Three conical shell geometries were considered: a 3-meter diameter 70 degree shell, a 3.7-meter 70 degree shell, and a 6-meter diameter 70 degree shell. The 6-meter configuration was loaded statically and the results were compared with an experimental load test of a 6-meter HIAD vehicle. Though agreement between theoretical and experimental strains was poor, circumferential wrinkling phenomena observed during the experiments was captured by the theory and axial deformations were qualitatively similar in shape. With piston theory aerodynamics, the nonlinear flutter dynamic pressures of the 3-meter configuration were in agreement with the values calculated using linear theory, and the limit cycle amplitudes were generally on the order of the shell thickness. Pre-buckling pressure loads and the aerodynamic pressure correction factor were studied for all geometries, and these effects resulted in significantly lower flutter boundaries compared with piston theory alone.

In the final phase of this work, the existing linear and nonlinear FTPS shell models were coupled with NASA's FUN3D Reynolds Averaged Navier Stokes CFD code, allowing for the most physically realistic flight predictions. For the linear shell structural model, the elastically-supported shell natural modes were mapped to a CFD grid of a 6-meter HIAD vehicle, and a linear structural dynamics solver internal to the CFD code was used to compute the aeroelastic response. Aerodynamic parameters for a proposed HIAD re-entry trajectory were obtained, and aeroelastic solutions were calculated at three points in the trajectory: Mach 1, Mach 2, and Mach 11 (peak dynamic pressure). No flutter was found at any of these conditions using the linear method, though oscillations (of uncertain origin) on the order of the shell thickness may be possible in the transonic regime. For the nonlinear shell structural model, a set of assumed sinusoidal modes were mapped to the CFD grid, and the linear structural dynamics equations were replaced by a nonlinear ODE solver for the conical shell equations. Successful calculation and restart of the nonlinear dynamic aeroelastic solutions was demonstrated. Preliminary results indicated that dynamic instabilities may be possible at Mach 1 and 2, with a completely stable solution at Mach 11, though further study is needed. A major benefit of this implementation is that the coefficients and mode shapes for the nonlinear conical shell may be replaced with those of other types of structures, greatly expanding the aeroelastic capabilities of FUN3D.

Dissertation

As the demand to improve the fuel efficiency of current commercial aircraft increases, new commercial airliner concepts such as the Blended Wing Body has been researched on and studied in various aspects over the years as an efficient alternative to the conventional transport configuration. One particular aspect of the Blended Wing Body is the use of the propulsive fuselage concept. In this concept, the fuselage boundary layer is ingested by the engine and this is aimed at producing benefits such as improved fuel efficiency, reduced ram drag as well as lower structural weight of the engine. During the ingestion process, the low momentum boundary layer is re-energized by the propulsion system before exiting into the atmosphere. In this way, the ingested flow does not contribute to the wake deficit and hence, the overall drag of the aircraft is reduced. Since thrust equal drag in steady and level flight, and power is equal to thrust multiplied by velocity, the reduction in drag implies a reduction in the power required to drive the vehicle.In essence, the ingestion of the boundary layer which leads to a lower inlet stagnation pressure represents a direct thermodynamic penalty. However, the momentum deficit captured by the engine represents a drag reduction to the aircraft. In this way, the propulsion system performance suffers a decrease in engine efficiency while the aircraft drag is reduced in proportion to the amount of boundary layer flow that is ingested. Therefore, a trade-off exists between the increase in aircraft drag reduction and the decrease in engine performance as more boundary layer is consumed. Another important concern is the significant flow distortion which can lead to increased vibration and fatigue of the fan and compressor blades in particular. This flow distortion is characterized by the distortion coefficient, a standard widely used in the aircraft engine industry. While it was found that the ingestion of the boundary layer can provide a decrease in fuel burn of several percentages, the benefits of boundary layer ingestion have shown to be very sensitive to the magnitude of the fan and duct losses. Hence, it is crucial that fan designers are able to design new rotor blades that are able to withstand the flow distortion while ensuring that engine performance degradation is kept to a minimum in order to maximize the overall gain in fuel efficiency.The main aim of this research is therefore to understand and analyse the rotor performance under both uniform and non-uniform inflow condition. This will then provide insights into the main fluid mechanism affecting rotor performance under such conditions. As such, the early phase of this research was focused on the development of an in-house blade modeller which was then later used in the parametrization and reconstruction of the NASA Rotor 67. Other than the development of the Blade Modeller, this research was also focused on the coupling of an open-source meshing software, SALOME to the Blade modeller which will then allow the user to achieve automated meshing needed for the design optimization process. The main highlight of this thesis is on the detailed analysis of the blade to blade domain as well as the overall rotor performance under non uniform inflow condition.

The aerospace industry has been concerned with propeller noise levels for years. This interest is two-fold: government regulation and comfort in cabin. This report attempts to create a simulation mechanism needed to evaluate the far-field noise generation levels. However, in order to do that, the tandem cylinder case was evaluated first as a validation step before the SR-7A propeller case was performed. Both cases use STAR-CCM+, a commercial software, to perform the simulations.

The space vehicle system concept (i.e. resupply vehicle) described is based on the new direction that President George W. Bush announced on January 14, 2004 for NASA’s Human Exploration, which has the space shuttle retiring in 2011 following the completion of the International Space Station (ISS). This leads to a problem for the ISS community regarding the capability of meeting a sixty metric-ton cargo shortfall in resupply and the ability of returning large payloads, experiment racks and any other items too large to fit into a crew only type spacecraft like the Orion or Soyuz. NASA and the ISS partners have realized these future problems and started developing various systems for resupply to ISS, but none offer the capability for large up or down mass close to that of the shuttle. Without this capability, the primary purpose behind the ISS science mission is defeated and the ability to keep the station functioning properly is at risk with limited payload delivery (i.e. replacement hardware size and mass). There is a solution to this problem and a majority of the solution has already been designed, built, and flight tested. Another portion has been studied heavily by a team at NASA for use in a slightly different mission. Following the retirement of the space shuttle fleet and the loss of heavy up and down mass capability, the only solution to the problem is to design a new spacecraft. However, the budget and new direction for NASA will not allow for a costly new payload carrying spacecraft. The solution is to use existing commercial off the shelf (COTS) hardware to minimize the costs of developing a totally new system. This paper will discuss the technical feasibility of this conceptual configuration.